Analysis of unknown biopolymer targets often involves their specific binding to known biopolymer probes. The most common technique employing immobilized biopolymers is the Southern blot hybridization technique, in which a set of DNA targets is immobilized on a membrane and a solution containing labeled DNA probe molecules is used to bathe the membrane under conditions where complementary molecules will anneal. In an analogous technique called Northern blot hybridization, RNA targets are immobilized on membranes and anneal to complementary RNA probes. Reverse blot hybridization employs the opposite approach. Instead of immobilizing DNA targets, a set of DNA probes is immobilized on a solid surface and the unknown labeled DNA target is present in the liquid phase.
Arrays, constructed by attaching a plurality of the same or different biopolymers to discrete isolated areas on the surface of a substrate, are becoming increasingly important tools in the analysis of biopolymers such as gene expression analysis, DNA sequencing, mutation detection, polymorphism screening, linkage analysis, genotyping, and screening for alternative splice variants in gene transcripts.
The analysis of microarrays depends considerably on spot quality, such as morphology and homogeneity, for obtaining high levels of accuracy and consistency. Quality control of common printing defects generated during the production of an array is critical to maintaining data integrity and preventing the wastage of reagent and labor. The ability to manufacture microarrays in an efficient and cost-effective manner is of considerable interest to researchers worldwide and of significant commercial value.
One important factor in the spotting process is the chemical properties of the solution in which the biopolymer is dissolved. With the widely used saline sodium citrate (SSC) buffer, binding efficiency and spot uniformity are often poor. The problems are reduced by supplementing SSC with 50% dimethyl sulfoxide (DMSO). However, this reaction buffer has the disadvantage of being toxic as well as being a solvent for many materials, in addition to only having a limited effect on spot appearance.
Considering the issues of spot morphology and quality control in spot arraying, there is still a need for a formulation of a spotting solution that will provide uniform spot size and/or morphology in the production of assay articles such as microarrays. There also remains a need for a means of non-destructive quality control of the production of such assay articles.